TheiPad, which resembles a giant iPhone, has a 9.7in full-colour touch-screen, and can be used to watch movies, surf the internet, listen to music, view photos, and read ebooks and digital versions of newspapers and magazines. Jobs described the device as a "truly magical and revolutionary product".

He confirmed speculation that the iPad could be used to read ebooks, newspapers and magazines. "Amazon has done a great job of pioneering books with the Kindle," said Jobs. "We're going to stand on their shoulders and go a bit further."

Apple has launched an ebook store, called iBook, that will allow users to purchase and download books on the go. Purchased books appear on a virtual bookshelf, complete with cover art, and the electronic pages resemble a real-life book. Jobs said Apple had signed deals with several major publishers, including Penguin and HarperCollins, and that he hoped other publishers would also make their content available on the platform.

The New York Times has developed an application, specially tailored for the iPad, which allows readers to view videos embedded within articles, and which recreates the look and feel of the print edition.

"The iPad combines the best of print with the best of digital, all rolled up in to one," said Martin Nisenholtz, a senior executive at the newspaper. "It's something you can really immerse yourself in. We're pioneering the next version of digital journalism."

Jobs said that Apple had been pondering whether or not to launch a tablet computer for years. "We asked, was there room for a third category of device, between laptops and smartphones?," he told journalists and analysts at the Yerba Buena Centre in San Francisco."If there's going to be a third category of device, then it has to be better at things like web browsing, email, sharing photos, watching videos, enjoying music, playing games and reading ebooks than a smartphone or laptop.

"What this device does is extraordinary. It's the best browsing experience you've ever had. You're holding the internet in your hands. It's way better than a laptop, it's way better than a smartphone. Using it is so much more intimate than a laptop, and so much more capable than a smartphone."

The iPad, which weighs 680g and is 1.3cm thick, has a 10 hour battery life and can surf the internet over Wi-Fi. It is available with 16GB, 32GB or 64GB of flash storage. Wi-Fi-only models will be available in UK in 60 days. In the US the WiFi-only models will be priced at $499 for 16GB model, $599 for 32GB model, $699 for 64GB model. 3G models will hopefully be available in the US in 90 days and in the UK later this year, when carrier deals are struck. These models will cost $629 (16GB), $729 (32GB), $829 (64GB)

Applications and games available in the App Store can be used on the iPad, and developers will also be able to build software specifically for the larger-screen device. Electronic Arts, one of the world's biggest video games studios, said it was developing a range of games for the platform, as are dozens of other games companies.

"The ability to run existing apps is critical, and puts the iPad in a different league to other devices," said Michael Gartenberg, a technology analyst. "Gaming on the iPad is going to be huge.”